Research is proposed in the following areas: 1. Thermodynamic studies will be carried out on the factors which affect the in vitro self-assembly of pure brain tubulin into microtubules. Particular attention will be paid to the effect of ligands and to the role of non-tubulin proteins which may complex with tubulin. 2. The interactions of anti-cancer drugs with tubulin and their effects on the modes and thermodynamics of tubulin self-association will be examined in detail, with particular attention on possible conformational effects. 3. The specific and non-specific interactions of solvent components with tubulin and other proteins will be investigated with particular attention on the manner in which they promote microtubule formation and participate in the isolation of tubulin by the cycle procedure. BIBLIOGRAPHIC REFERENCES: A Solution Physical-Chemical Examination of the Self-Association of Tubulin, S.N. Timasheff, R.P. Frigon, and J.C. Lee, Federation Proc. 35, 1886 (1976). The Interaction of Tubulin and Other Proteins with Structure-Stabilizing Solvents, S.N. Timasheff, J.C. Lee, E.P. Pittz, and N. Tweedy, J. Colloid and Interface Sci. 55, 658 (1976).